Many of the factors regulating growth and development appear to be conserved between vertebrates and invertebrates. The ease with which certain well studied invertebrates can be manipulated both genetically and experimentally greatly facilitates detailed studies of how these factors operate. Although the genetics and development of C. elegans has been among the most extensively characterized, current molecular studies have been hampered by the lack of DNA transformation techniques for assaying the function of cloned genes in vivo. This project proposes (i) to develop techniques for gene transfer into C. elegans and (ii) to use those techniques to analyze muscle cell development. In the Preliminary Results section, new techniques are presented which allow foreign sequences to be inserted into the C. elegans genome, yielding transgenic lines of animals that express the integrated DNA. These techniques will be used to introduce several cloned muscle specific genes, and to determine which sequences are responsible for tissue specific expression. Once these cis-acting sequences have been identified, the trans-acting factors which interact will be identified by biochemical and/or genetic techniques. The eventual goal is to find the elements responsible for the segregation of developmental potential during the early embryonic division. At the same time, continued improvements in DNA transformation techniques will be sought. These include increases in the frequency of stable transformation, and attempts to utilize transposon vectors or homologous recombination to permit greater control over the structure of the integrated DNA and site of integration. In addition, gene fusions between cloned myosins and a variety of marker polypeptides will be constructed. The identification of a marker system suitable for C. elegans muscle should greatly facilitate the analysis of muscle gene expression described above.